mwifiex: display correct country information in debugfs "info"

Use "priv->country_code" string to display country information in
debugfs command "info" instead of "adapter->region_code".

"adapter->region_code" contains default region code got from FW while
initialization, whereas "priv->country_code" is updated in reg_notifier
handler whenever there is a change in regulatory domain.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kiran Divekar <dkiran@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>